Field of the Invention
The present invention relates to a sheet feeding apparatus that feeds sheets to an image forming apparatus, and an image forming system that has the sheet feeding apparatus and the image forming apparatus. Particularly, the present invention relates to a sheet feeding apparatus that stores envelopes.
Description of the Related Art
Conventionally, there has been known a sheet feeding apparatus that feeds sheets to an image forming apparatus such as a copying machine, a printer apparatus, a facsimile apparatus, a printing machine, and a composite machine. The sheet feeding apparatus is connected to the image forming apparatus when used as an image forming system.
In recent years, there has been known an image forming system that stores, in a sheet feeding apparatus, envelopes as sheets, and forms an image on the envelopes. Since the envelope is formed in a bag shape, a pasted portion in which the sheet is overlapped and stuck is formed not only on a bottom side opposite to an opening side on which a flap portion is formed, but in the center in a width direction perpendicular to a conveying direction in the envelope (so-called center pasting) or on one side in the width direction (so-called corner pasting).
Therefore, when a number of envelopes are stored in the sheet feeding apparatus, and the envelopes are stacked, a pasted portion side in the envelopes becomes higher than a non-pasted part, and a topmost envelope inclines with respect to a horizontal surface. As a result, there is caused an disadvantage that the envelopes cannot he accurately conveyed to a conveying portion that conveys the envelopes to the image forming apparatus.
In order to solve such an disadvantage, there is disclosed in the sheet feeding apparatus described in Patent Literature 1, for example, a sheet feeding apparatus including a sheet feeding auxiliary plate that can be deformed in accordance with an inclination of the stacked envelopes. In the sheet feeding apparatus described in Patent Literature 1, the sheet feeding auxiliary plate including a pair of triangular plates is deformed using a plurality of cylinders.